We have observed a consistent metabolic defect in cell-to-plasma cholesterol transport in several categories of human subject. These show no common feature of major lipoprotein concentration or composition but are all at high risk for atherosclerotic vascular disease. An inhibition of cholesteryl ester transfer is associated with development of an apo E-dependent shunt pathway bypassing lecithin: cholesterol acyltransferase (LCAT). Affected groups include patients with familiar hypercholesterolemia, non-insulin-dependent diabetics, and those with familiar hypertriglyceridemia associated with documented vascular disease and progeria. In this proposal we would like to determine whether this metabolic abnormality is also shared by other groups of diabetics. We will assay the reaction rates and reactant concentrations of components of the cell-to-plasma cholesterol transport gradient (cholesterol carrier lipoprotein; lecithin:cholesterol acyltransferase; cholesteryl ester transfer) in untreated diabetics, and diabetics whose plasma glucose and lipids are normalized with improved metabolic control with insulin. Additionally the structure, composition and metabolic interations of the diabetic acceptor lipoproteins, before treatment and after normoglycemia, will be studied. The composition of the apo E-containing shunt lipoprotein fraction will be studied by immunoaffinity chromatography. Using specific immobolized antibodies to lipoprotein apoproteins, the stoichiometry and concentration of this fraction will be determined. Bound lipoproteins will be separated for further analysis using newly developed mild desorption techniques. Finally we will study the extent to which diabetic blood cells and platelets may be modified in ways that relate to their ability to promote cholesterol transport. The possible existence of specific influx sites for apo E-transported free cholesterol will be assayed. The normalization of cholesterol transport by metabolic control with insulin in diabetics offers an opportunity to study the mechanism of this defect of lipid metabolism. The results appear to have major relevance to the basic biochemistry of atherogenesis in human subjects.